How does the Garbage Collector determine that an object is no longer used and can be removed from memory?

Garbage Collector (GC) in Android (and in Java in general) determines that an object is no longer in use through a reachability algorithm.

How it works:

• GC starts with root objects, such as local variables in the stack, static fields, etc.
• It traverses all objects that are referenced from the roots.
• All objects that cannot be reached through a chain of references from the roots are considered unreachable.
• Unreachable objects are considered garbage and can be removed from memory.

Example: if an object is not stored in any variable, not passed to methods, and not contained in other objects, GC will identify it as unused and free the memory.